Automatic measurement system of tire tread length based on image processing

To measure the tire tread length on-line automatically, a length measurement system was established for the tire tread, and image processing and measuring algorithms used in productive process were investigated. For the purpose of removing the influence of light in a real field, several methods such as median filtering, gray stretching etc, were used to preprocess the image, and the OSTU algorithm was used to accomplish the image binary process. The edge of the tire tread is straight line, so linear fitting algorithm was used to fit the linear equation in the image plane. To avoid the inconvenience in installation caused by calibration on the site, a couple of measurement reference points were reserved. The coordinate transformation parameters were obtained using the multiple linear regression method. The line equation of the tread head and the tread tail in the physical coordinate system were determined by the coordinate transformation. Therefore, the length of tire tread could be calculated. Experimental results indicate that the precision of the measuring system proposed in this paper is less than or equal to 2 mm for multiple measurement of various tire treads, and the 3σ value is less than 1.1 mm. Although the tire tread is elastomeric, the measuring system can satisfy the production requirement. The system is characterized by convenient installation and testing, system stable operation, etc. © 2015, Chinese Academy of Sciences. All right reserved.